Controlled Sensor\nDerived from COF Materials for the\nEffective Detection of <i>N</i>‑Methylpyrrolidone

<i>N</i>-methylpyrrolidone (NMP) is an excellent\nadvanced\nsolvent that can be easily absorbed by the human body and has the\ncharacteristics of flammability and explosion. To reduce the risk,\nthe environmental concentrations of NMP need to be measured. A series\nof covalent organic frameworks (COF) connected by an imine bond have\nbeen successfully prepared at room temperature by changing the synthesis\ntime catalyzed by scandium(III) trifluoromethanesulfonate (Sc(OTf)<sub>3</sub>). The effect of the synthesis time on the sample properties\nwas compared by XRD, FT-IR, XPS, SEM, TEM, and BET. The results showed\nthat synthesis time had almost no effect on the morphology, specific\nsurface area, and functional groups of the COF samples but had a significant\nimpact on the pore size distribution, residual bonds, and other defects,\nwhich in turn affected the gas sensing performance. The sensor results\nshowed that all samples had good sensing performance for NMP, among\nwhich the sample synthesized for 48 h had the best sensing performance,\nwith a limit of detection of 692 ppb and good stability and repeatability.\nThe excellent performance of the COF samples benefits from the large\nspecific surface area, hydrogen bonding interactions, electrostatic\nattraction, and high defects. This study provides an effective method\nfor NMP detection and expands the application range of the COF materials.